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Doctoral Thesis
DOI
10.11606/T.76.1995.tde-24032015-115318
Document
Author
Full name
Maria Cristina Andreolli Lopes
Institute/School/College
Knowledge Area
Date of Defense
Published
São Carlos, 1995
Supervisor
Committee
Iga, Ione (President)
Abatte, Miguel
Bagnato, Vanderlei Salvador
Brescansin, Luiz Marco
Trsic, Milan
Title in Portuguese
Transições eletrônicas em átomos e moléculas por espectroscopia por perda de energia de elétrons. Desenvolvimento de aparelhagem e estudos experimentais
Keywords in Portuguese
Não disponível
Abstract in Portuguese
Este trabalho se constitui de duas partes principais. A primeira delas envolve o desenvolvimento de um Espectrômetro de Perda de Energia de Elétrons (EPEE), dotado de alta resolução e feixe eletrônico monocromatizado. As energias de impacto abrangem a faixa de 50 a 500 eV e a variação angular o intervalo de 50° a + 50°. O EPEE emprega como elemento dispersivo Analisadores Dispersivos Cilíndricos de 127° (ADC 127°), associado a lentes eletrostáticas desaceleradoras e aceleradoras. São discutidos os princípios de funcionamento dos elementos do EPEE, seu projeto e modo operação. O teste de desempenho do EPEE se fundamentou na comparação de espectros de perda de energia de elétrons com ele obtido, para as amostras gasosas Argônio, Hélio, Neônio, Nitrogênio molecular, com dados publicados na literatura. Em alguns desses espectros obteve-se a resolução de 109 meV. A segunda parte do trabalho consiste no estudo espectroscópico da camada de valência do Tetrafluoreto de Carbono, CF4 , onde se observa pela primeira vez a transição proibida por dipolo 1e → 3s. Adicionalmente, relata-se a obtenção de um espectro relativo de fotoabsorção, através da aplicação do método de conversão Bethe- Bom a espectros de perda de energia de elétrons obtidos para o CF4
Title in English
Not available
Keywords in English
Not available
Abstract in English
The scope of this work consists of two main themes. In the first part it is described the development of an Electron Energy Loss Spectrometer (EELS) for operation at high resolution, in the impact energy and angular ranges from 50 eV to 500 eV and from -50° to +50° respectively. The apparatus makes use of 127° Cylindncal Dispersive Analyzers (ADC- 127°) and accelerating and decelerating electrostatic lenses. We discuss in this work the physical principles concerning the EELS, its project and the its operation. The EELS's performance is appraised through the reproducibility of Electron Energy Loss Spectra for Ar, He, He and N2 gases obtained with our apparatus and others published in the literature. In some of these studies an energy resolution of 109 meV (FWHM) was reached. In the second part, spectroscopy studies of the valence excitation shell were conducted for CF4. In these studies we report the first observation, of a dipole forbidden transition (1e → 3s) at 14.77eV. From the electron energy loss spectrum, a relative photo-absorption spectra of CF4 was also obtained using the Bethe-Born Method
 
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Publishing Date
2015-03-25
 
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